Intra-Group Lethal Gang Aggression in Domestic Pigs (Sus scrofa domesticus)
Institute of Genetics and Animal Biotechnology, Polish Academy of Sciences, Ul. Postępu 36A, Jastrzębiec, 05-552 Magdalenka, Poland
Animal Behaviour & Welfare, Department of Animal and Veterinary Sciences, Scotland’s Rural College (SRUC), West Mains Rd., Edinburgh EH9 3JG, UK
Institute of Animal Welfare Science, Department of Farm Animals and Veterinary Public Health, University for Veterinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria
Pig Development Department, Teagasc, P61 P302 Moorepark, Ireland
Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
Author to whom correspondence should be addressed.
Received: 12 June 2020 / Revised: 20 July 2020 / Accepted: 24 July 2020 / Published: 28 July 2020
Aggression between pigs in pig husbandry is common during regrouping but rare in stable social groups. Farmers report the occurrence of lethal gang aggression in stable groups of pigs, whereby the group attacks one group member until it is dead. Our aim was to document this extreme type of aggression and to identify potential causes. Forty-two farmers, experiencing lethal gang aggression or not, filled out a survey about their farm management. From 91 victims, information was obtained on their injuries and body condition. Gang aggression occurred more on farms with deep straw bedding, a housing type commonly associated with better animal welfare. However, the presence of straw may also be related to other factors, which could not be disentangled here. Gang aggression did not relate to the genetic line, breeding company or feed type. It equally occurred between females and males and tended to occur more in winter. Victims were covered in injuries, but had a healthy body condition, whereas survivors had a lower body condition. Overall, the cause seems multi-factorial, and further research on the occurrence of lethal gang aggression is needed.